The aim of this study was to examine whether the neonatal injection of capsaicin induces DNA ladder formation, as an indicator of apoptosis, in the rat trigeminal ganglion (TG). The DNA extracted from the TGs after treatment with capsaicin (50 mg/kg) at 2 days of age exhibited diffuse DNA fragmentation instead of “ladder formation”, as determined by agarose gel electrophoresis. In contrast, clear DNA ladder formation was induced in human osteosarcoma cells treated with okadaic acid (OA) at concentrations of 10 and 20 nM. These results suggest that capsaicin cannot induce apoptosis of TG neurons sufficient for detectable DNA ladder formation. Thus, it is conceivable that capsaicin mainly causes necrosis rather than apoptosis in rodent primary sensory neurons.

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